Technical / Research - Page 1

Researchers from the University of California Berkley developed a new flexible and lightweight blood oxygen sensor that can map oxygen levels over large area. The sensor uses an array of red and near-infrared OLEDs, together with organic photo-diodes, printed on a flexible substrate.

The research was supported by Cambridge Display Technology, which means that these red and near-infrared printed OLEDs use polymer emitters (PLEDs).

Researchers from Korea's KAIST research institute developed a high-efficiency OLED architecture that uses external scattering medium to achieve an EQE greater than 50%.

Such high EQE was only demonstrated before using complex internal nanostructures or by employing a micro-lens array, but these solutions are complicated to produce and can hinder the OLEDs flexibility and planar structure. The researchers say that their scattering approach maintains the planar geometry , results in flexible OLEDs and can be easily scaled to enable low cost production.

The UK innovation agency (Innovate UK) has launched a new 30-month project called UltraWELD, which aims to improve airtight bonding in OLED lighting for aerospace and defense applications. The project partners will develop photonic-based processes for highly dissimilar material joining.

Current dissimilar materials joining is mainly done using adhesive bonding - a highly flexible and low cost process, but one that cannot provide truly hermetic bonds, which reduces the performance of the panels and can lead to optical damage.

Researchers from the Fraunhofer FEP institute developed a new micro-patterning process using an electron beam to produce OLED microdisplays on silicon substrates. This could enable a new way to produce direct-emission OLED microdisplays, which will be more efficient and bright compared to the current ones that use color filters.

The electron beam patterning is performed after the encapsulation step - the beam goes through the encapsulation layer and can be used to modify the emission of the OLED materials. To create red, green, and blue pixels, an organic layer of the OLED itself is ablated by a thermal electron beam process.

Researchers from Japan's Kyushu University developed a new technology called singlet fission that enables near-infrared OLED materials to surpass the 100% limit for exciton production - or achieve an internal quantum efficiency (IQE) of over 100%. Singlet fission was already used in OPVs, but this is the first time that it was demonstrated with OLEDs.

Achieving over 100% is possible because at 100% IQE all charges form excitons that emit light. The new technique splits the energy from a high-energy excitons into two low level ones. The new OLED emitter materials use molecules in which singlets can transfer half of their energy to neighboring molecules while keeping half of the energy for themselves - each singlet creates two triplets. The emitters emit near-infrared light.

The Fraunhofer FEP announced that it developed a new technology to produce ultra-smooth polymer films. The new technology can be used to produce low-defect density films in a roll-to-roll based process, suitable for a wide range of applications - including encapsulation films, touch layers and as OLED substrates.

This technology was developed as part of the EU-funded OptiPerm project. The Fraunhofer researchers say that this new innovative process does not require any special processing environment and could be used under standard factory conditions.

Motorola has been granted an interesting patent that aims to solve screen deformation with foldable displays. Motorola says that one of the issues with foldable displays is that they deform in low temperatures.

Motorola suggests using a temperature sensor that detects when the display is deformed, and then the hinge is heated so that the display is automatically corrected. This could be used to create foldable OLEd phones that bend both inward and outwards, and can work with more than one hinge (so that you can fold a display several times).

Researchers from the Universitat Autònoma de Barcelona and TU-Dresden have demonstrated that ultra-stable film formation can be used to to improve the performance of OLED devices.

The researchers grew (using evaporation) the organic materials as ultrastable glasses - a growth condition that allows for thermodynamically most stable amorphous solids. Testing four different phosphorescent emitters, the researchers show significant (over 15%) increases of efficiency and operational stability. The researchers also say that these growing conditions are expected to even be more useful for TADF materials.

Researchers from the University of Michigan developed a new method to cost-effectively extra more light out of OLED displays. To achieve that, the researchers used a Sub-Electrode Micro-Lens Array (SEMLA) placed between the bottom transparent ITO electrode and the glass substrate. Testing on green and white PHOLEDs, the researchers say the SEMLA enhanced light output by a factor of 2.8 (green) and 3.1 (white) compared to a similar device without the lens array.

The researcher say that such an array can be fully transparent and has no impact on the sharpness of the display. The hexagonal array of 10 μm lenses can be fabricated using conventional photolithography methods which are quite cost effective. Such a micro-lens array does not change the actual OLED production process.